Objective To make a comparison for the neutrophils prepared either by induction of differentiation of myeloid leuke-mia cell line,or by separation and purification of peripheral blood cells,or by induction of myeloid differentiation of peripheral blood stem cells.Methods NB4 cells were induced differentiation by 1μmol/L all-trans retinoic acid (ATRA)to mature granulo-cytes;neutrophils were separated and purified from peripheral blood by lysis of red blood cells followed by negative selection using magnetic bead-labeled antibodies;hematopoietic stem cells were separated and purified from peripheral blood by Percoll gradient centrifugation followed by negative selection using magnetic bead-labeled antibodies,and were induced to myeloid differentiation by GM-CSF and G-CSF.Morphology and purity of neutrophils prepared by these three methods were studied by means of MGG stai-ning.CD18 protein expression and subcellular distribution were studied by means of immunofluorescence staining.Results Purity of neutrophil was above 40% by induction of differentiation of NB4 cells,and was about 90% if purified from peripheral blood,and was above 70% if induced by myeloid differentiation of peripheral blood stem cells.There was no obvious difference for CD18 ex-pression in neutrophils prepared by these three methods,and staining of CD18 had a dotted pattern distributed in these cells.Con-clusion Peripheral blood neutrophils prepared by lysis of red blood cells followed by negative selection using magnetic bead-labeled antibodies are with high purity and viability which is suitable for immediate test of neutrophils from fresh blood.Neutrophils pre-pared by myeloid differentiation of hematopoietic stem cell are with high viability and last for days,which can be used in long test for neutrphils.

Objective:To investigate the application of digital teaching system in the teaching of onlay abutment teeth preparation for trainees receiving standardized residency training of stomatology (abbreviated as "resident trainees").Methods:The digital simulation teaching system unit was established by using the tissue morphology memory characteristics of 3Shape Trios oral scanner and Geomagic Control X 3D imaging design software. Eighteen resident trainees from the Daping Hospital were randomly divided into two groups, nine in the control group, preparing the onlay resin tooth model independently after taking the routine PPT + demonstration operation teaching; the other nine in the test group, preparing onlay model after learning digitization teaching system unit. All resident trainees prepared on three models respectively. After the teaching, the amounts of preparation and polymerization degree were compared between the two groups, making a summary teaching evaluation. Amounts of preparation, polymerization degree and teaching satisfaction were tested by independent-samples t-test with software SPSS 21.0. Results:Compared with the resident trainees in control group, the t values of width difference of buccal shoulder, lingual shoulder, proximal middle shoulder and distal middle shoulder, height difference of functional cusp and the lowest part of the proximal middle fossa, and degree of buccal polymerization, lingual polymerization and distal polymerization were 6.21, 6.12, 3.83, 4.73, 3.73, 4.79, 8.35, 4.35, and 6.69 respectively , while P values were respectively as <0.001, <0.001, <0.001, <0.001, 0.001, <0.001, <0.001, <0.001, and <0.001, with statistical difference ( P<0.05) . The t values of height difference of non-functional cusp, the lowest part of the distal middle fossa and degree of proximal polymerization were 1.02, 1.97, and 1.43, while P values were respectively 0.312, 0.054, and 0.158, with no statistical difference ( P>0.05). All indicators of teaching satisfaction were statistically significant ( P<0.05). Conclusions:The application of digital teaching system is conducive to improving the onlay abutment teeth preparation level of residents with high teaching satisfaction, which is worth promoting in clinical practice.